Electric motors and methods of manufacturing the same are well known. A core (also known as a rotor core) of the motor comprises stacked and coined together laminates. Each individual laminate defines a center opening for connecting a shaft and a series of evenly spaced openings around the periphery of the laminate. The openings can have any suitable configuration. The laminates are stacked and coined in a sequential and slightly offset fashion such that the openings around the periphery define a spiral channel passing along the longitudinal axis of the core/rotor. This channel passes along the longitudinal axis in a helix or spiral fashion that enhances the motor performance. The rotors cores are heat treated to form a surface comprising magnetite Fe304. After heat treating, the channels are injected with molten aluminum thereby encapsulating the rotor within aluminum. The aluminum is typically injected at a temperature of about 1,300 to about 1,400 F and at a pressure of about 4,000 to about 6,000 psi.
There is a problem in this art associated with injecting the aluminum within the channels. It is believed that the aluminum can solder to the steel and form an electrical connection between the laminates, e.g., as detailed in “A Description of the Functions and Process Tests For Cast Aluminum Induction Motor Squirrel Cage Rotors” by J. Johnson et al., presented as a paper at Rotor Technology '86, Feb. 5-7, 1986, the disclosure of which is hereby incorporated by reference. Such an electrical connection can cause a short within the electric motor thereby reducing, if not eliminating, the effectiveness of the electric motor. There is a need in this art for an electric motor fabrication method that isolates the aluminum from the laminates e.g., prevents the molten aluminum from infiltrating between the stacked/coined laminates (with or without a magnetite surface).
There is also a need in this art to improve electric motor manufacturing by employing the principals known as “lean manufacturing” in order to eliminate non-value added activities during the manufacturing process. Examples of non-value added activities are described in U.S. Pat. No. 5,161,597 (Dohoger) and U.S. Pat. No. 5,488,984 (Fahy), e.g., burn-off ovens, oxidation furnaces, hot drop, among other processing delays. By improving electric motor manufacturing and employing statistical process controls, the amount of work in progress can be reduced and “just in time” production methods can be adopted.
As described in U.S. Pat. No. 5,488,984, rotors of electric motors can be coated with sodium nitrate. Other conventional coatings compositions and methods for treating metals are disclosed in U.S. Pat. Nos. 4,870,814; 4,032,366; 5,182,963; 5,776,261; 3,839,256; 3,372,038; 2,641,556; 2,803,566; 5,723,181; 2,554,250; 1,068,410; 2,811,473; 2,282,163; 3,910,797; 3,832,204; 3,917,648; 2,978,361; 5,789,085; 3,796,608; 3,133,829; 2,385,332; 2,799,658; 2,641,556; 3,839,256; and 3,752,689.
Magnetic Silicon Steels produced for use as laminates either for rotor, stator or transformer application typically require an annealing separator comprising thin films of inorganic compounds such as magnesium oxide and phosphate as taught by J. Evans in U.S. Pat. No. 3,615,918 and Akerblom in U.S. Pat. No. 4,120,702 and Nakayama U.S. Pat. No. 4,875,947 and magnesium from U.S. Pat. No. 2,385,332 V. Carpenter, and Steger in U.S. Pat. No. 3,583,887, sodium silicate Lee in U.S. Pat. No. 3,945,862 teaches an amorphous magnesia silica complex and a boron bearing compound. Evans teaches an insulation coating for electrical steels in U.S. Pat. No. 3,996,073 comprising an aluminum magnesium phosphate solution with colloidal silica and chromic anhydride. Organic quaternary ammonium silicate coatings are taught by R. Parkinson, U.S. Pat. No.3,839,256 and polyvinyl acetate with phosphoric acid and chromic acid is taught by Kitayama in U.S. Pat. No.3,793,073. Additionally, Yamazaki, in U.S. Pat. No. 5,961,744 teaches colloidal silica and aluminum phosphate. Haselkom in U.S. Pat. No. 4,496,399 teaches silica and aluminum silicate dispersed in vinyl resins, while Morito in U.S. Pat. No. 4,255,205 teaches silicate aluminum oxide, strontium and barium compounds in phosphoric acid. B. Perfetti in U.S. Pat. No. 4,507,360 teaches magnesium silicate, mica, titanium oxide and alkali metal borate. Perfetti also teaches in U.S. Pat. No. 4,517,325 the use of organic quaternary ammonium silicate and ethylene/acrylic or ethylene/vinyl/acetate copolymer a small amount of barium, strontium or lead chromate. Katayama in U.S. Pat. No. 4,844,753 teaches acrylic and a acrylic styrene resins with chromates. Nakamura in U.S. Pat. No. 4,618,377 also teaches emulsions. U.S. Pat. No. 1,951,039 by Scharschu, teaches sodium silicate, lime and iron oxide. D. Loudermilk teaches inorganic/organic insulating films in U.S. Pat. No. 5,955,201 utilizing aluminum silicate, aluminum potassium silicate and magnesium silicate dispersed in a water-soluble, organic solvent, resin. Also acrylic resin with chromates are taught by K. Kenichi in U.S. Pat. No. 4,844,753. Also Robinson teaches a paint in U.S. Pat. No. 2,641,556 comprising refractory material suspended in a solution of a decomposable binder such as a solution of an alkyd resin, cellular acetate in organic solvents. U.S. Pat. No. 5,922,413 by Takeda, teaches a method of coating a rotor core by applying a liquid primer followed by applying a powder coat. The disclosure of the previously identified U.S. Patents and publications is hereby incorporated by reference.